Also known (around Coolmath, anyway) as Guzzinta Tests.

Here are some quick tricks you can learn to see if a number is divisible (can be divided by) another number.  Huh?

OK...  You can see that 18 is divisible by 3... meaning that 3 goes into 18.

Remember your guzzintas?

3 guzzinta 18 six times!  ( 3 goes into 18 six times. )

That's an easy one, since it's from our times tables.

But, can you quickly tell if 3 goes into 237?  Without doing long division?  I can!  And not just because I'm a super math geek -- because I know some cool tricks!  These are good to learn because they will save you lots of time!

Divisibility by 2 Test:

A number is divisible by 2 if it is even.

Here's another way to phrase this one:

A number is divisible by 2 if
it's last digit is
0, 2, 4, 6, or 8

Let's do an easy one from our times tables:

Does 2 go into 16?  ( Is 16 divisible by 2? )
Yes, since the last digit is 6.  ( It's even! )